Bearing assemblies are typically employed to provide support for a sliding or rotating movement of an element with minimum friction, and more typically to permit rotation of a rotatable shaft element, such as to provide support of a high-speed spindle, disc-drive shaft for computer magnetic disc operations. Magnetic liquids, more typically known as ferrofluids, have been employed with bearing assemblies for the entrapment of air or gas between a ferrofluid seal, so as to provide for a compressed gas between a rotating spindle and a stator, such as set forth, for example, in U.S. Pat. No. 3,734,578, issued May 22, 1973, and U.S. Pat. No. Re. 27,955, reissued Apr. 2, 1974. Such bearing assemblies disclosed in such patents are designed to be low-torque bearing assemblies, and very little ferrofluid is sheared. Such bearing assemblies are typically employed in movement of instruments and are not designed to withstand very high loads and, therefore, are generally "soft bearing-type" applications which entrap gases and use small amounts of ferrofluid and do not provide for the shearing of the ferrofluid.
Ferrofluids, also called ferrolubricants which exhibit lubricant properties, have been employed also in shearing-type ferrohydrodynamic low-friction-bearing assemblies. For example, U.S. Pat. No. 3,746,407, issued July 17, 1973, discloses a hydrodynamic bearing wherein a ferrofluid is employed both as a seal and as a ferrolubricant, and which bearing assembly includes grooves to provide for a pumping action of the ferrofluid. U.S. Pat. No. 3,726,574, issued Apr. 10, 1973, provides for a ferrohydrodynamic bearing with the use of ferrofluid as a seal, and with compensation means to provide for an adjustment in volume response to temperature. U.S. Pat. No. 3,780,593, issued Dec. 25, 1973, describes a rather complex, magnetic fluid, hydrodynamic bearing which creates a magnetic flux in the vicinity of the bearing, and which employs a ferrofluid and is typically designed for use in a gyroscope. U.S. Pat. No. 3,918,773, issued Nov. 11, 1975, is directed to a ferrofluid thrust bearing employing a ferrofluid seal. U.S. Pat. No. 4,254,961, issued Mar. 10, 1981, also describes a ferrofluid bearing assembly, wherein the ferrofluid is employed as a seal.
It is desirable to provide a ferrofluid thrust and radial bearing assembly particularly for use with precision high-speed shafts, such as in the computer-disc-drive industry or in textile spindles, which bearing assembly is of simple construction, is easily manufactured at low cost and which overcomes some of the disadvantages of the prior-art thrust and radial bearing assemblies.